Gamma Ray And Neutron Dosimeter

ABSTRACT

A dosimeter includes a housing and a printed circuit board positioned within the housing. A silicon photomultiplier is operably connected to the printed circuit board. A scintillator formed of Ce-activated lithium aluminosilicate glass is positioned on the silicon photomultiplier. An optical coupling is positioned between the scintillator and the silicon photomultiplier, and an optical reflector surrounds the scintillator.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the priority benefit from U.S. PatentApplication Ser. No. 62/749,232, filed Oct. 23, 2018, which is herebyincorporated by reference herein in its entirety for all purposes.

FIELD

Aspects of this disclosure relate generally to a gamma ray and neutrondosimeter, and more particularly, to a gamma ray and neutron dosimeterusing a solid-state scintillator of Ce-activated lithium aluminosilicateglass.

BACKGROUND

Gamma ray and neutron detectors or dosimeters are known for determiningradiation levels in an environment, which is useful in helping toprotecting users from exposure to such radiation. Gamma ray and neutrondosimeters exploit atomic or molecular excitation produced by radiationpassing through a scintillation material. Subsequent de-excitationgenerates photons that can be measured to give an indication of theenergy deposited in the dosimeter by the radiation.

A dosimeter includes scintillation material coupled to aphotomultiplier. When the dosimeter is exposed to radiation, thescintillation material is excited, generating photons of visible light.This light then strikes the photomultiplier, which generates a signalthat can be measured.

Known combination dosimeters used to measure both gamma rays andneutrons are often bulky, complicated to manufacture, and expensive. Oneexemplary combination dosimeter includes three pin diodes and threesignal processing detector paths.

It would be desirable to provide a combined gamma ray and neutrondosimeter that reduces or overcomes some or all of the difficultiesinherent in prior known devices. Particular objects and advantages willbe apparent to those skilled in the art, that is, those who areknowledgeable or experienced in this field of technology, in view of thefollowing disclosure and detailed description of certain embodiments.

SUMMARY

In accordance with a first aspect, a dosimeter may include a housing anda printed circuit board positioned within the housing. A siliconphotomultiplier may be operably connected to the printed circuit board.A scintillator formed of Ce-activated lithium aluminosilicate glass maybe positioned on the silicon photomultiplier. An optical coupling may bepositioned between the scintillator and the silicon photomultiplier, andan optical reflector may surround the scintillator.

In accordance with another aspect, a dosimeter may include a housingformed of metal. A printed circuit board may be positioned within thehousing, with a cable operably connected to the printed circuit boardand configured to supply power to the printed circuit board and providedigital data communication with the printed circuit board. A siliconphotomultiplier may be operably connected to the printed circuit board.A scintillator formed of Ce-activated lithium aluminosilicate glass maybe positioned on the silicon photomultiplier. An optical coupling formedof glue may be positioned between the scintillator and the siliconphotomultiplier. An optical reflector may surround the scintillator. Agadolinium filter may surround the scintillator and the photomultiplier.

In accordance with other aspects, a dosimeter system may include acomputer network having a plurality of computing devices. Each of aplurality of dosimeters may include a housing, a printed circuit boardpositioned within the housing and configured to communicate with thecomputer network, and a silicon photomultiplier operably connected tothe printed circuit board. A scintillator formed of Ce-activated lithiumaluminosilicate glass may be positioned on the silicon photomultiplier.An optical coupling may be positioned between the scintillator and thesilicon photomultiplier. An optical reflector may surround thescintillator. A plurality of repeaters may be configured to receive datafrom the dosimeters and transmit that data to the computer network.

These and additional features and advantages disclosed here will befurther understood from the following detailed disclosure of certainembodiments, the drawings thereof, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages of the presentembodiments will be more fully understood from the following detaileddescription of illustrative embodiments taken in conjunction with theaccompanying drawings in which:

FIG. 1 is a perspective view of a combined gamma ray and neutrondosimeter.

FIG. 2 is a perspective view of the scintillator and photomultiplier ofthe dosimeter of FIG. 1, shown with a filter.

FIG. 3 is a perspective view of the scintillator and photomultiplier ofthe dosimeter of FIG. 1, shown with an alternative embodiment of afilter.

FIG. 4 is a perspective view of an alternative embodiment of thescintillator of the dosimeter of FIG. 1.

FIG. 5 is a perspective view of an alternative embodiment of thescintillator of the dosimeter of FIG. 4.

FIG. 6 is a schematic view of a facility including a plurality of thedosimeters of FIG. 1 and a plurality of repeaters.

FIG. 7 is a schematic view of a network used in the facility of FIG. 6.

The figures referred to above are not drawn necessarily to scale, shouldbe understood to provide a representation of particular embodiments, andare merely conceptual in nature and illustrative of the principlesinvolved. Some features of the gamma ray and neutron dosimeter depictedin the drawings have been enlarged or distorted relative to others tofacilitate explanation and understanding. The same reference numbers areused in the drawings for similar or identical components and featuresshown in various alternative embodiments. Gamma ray and neutrondosimeters as disclosed herein would have configurations and componentsdetermined, in part, by the intended application and environment inwhich they are used.

DETAILED DESCRIPTION OF EMBODIMENTS

In the following description of various example structures in accordancewith the disclosure, reference is made to the accompanying drawings,which form a part hereof, and in which are shown by way of illustrationof various structures in accordance with the disclosure. Additionally,it is to be understood that other specific arrangements of parts andstructures may be utilized, and structural and functional modificationsmay be made without departing from the scope of the present disclosure.Also, while spatial terms such as “top” and “bottom” and the like may beused in this specification to describe various example features andelements of the disclosure, these terms are used herein as a matter ofconvenience, e.g., based on the example orientations shown in thefigures and/or the orientations in typical use. Nothing in thisspecification should be construed as requiring a specific threedimensional or spatial orientation of structures in order to fall withinthe scope of this disclosure.

Referring to FIG. 1, a combined gamma ray and neutron dosimeter 10includes a housing 12. In certain embodiments, housing 12 issubstantially light impermeable in order to prevent ambient light fromaffecting the performance of dosimeter 10, and may be formed of metal insome embodiments. For example, housing 12 may be formed of aluminum.Other suitable metals and materials for housing 12 will become readilyapparent to those skilled in the art, given the benefit of thisdisclosure.

The term “substantially” as used herein is meant to mean mostly, oralmost the same as, within the constraints of sensible, commercialengineering objectives, costs, manufacturing tolerances, andcapabilities in the field of gamma ray and neutron dosimetermanufacturing and use. Similarly, the term “approximately” as usedherein is meant to mean close to, or about, a particular value, withinthe constraints of sensible, commercial engineering objectives, costs,manufacturing tolerances, and capabilities in the field of gamma ray andneutron dosimeter manufacturing and use.

Housing 12 may include a cap 14 secured to a top of housing 12 thatseals the components of dosimeter 10 within housing 12. Cap 14 may besecured to housing 12 with an epoxy, glue or other sealing material inorder to provide protection from dust, water, moisture, or othercontaminants for the components of dosimeter 10. In certain embodimentscap 14 is secured to housing 12 with a black epoxy, but may be securedby other means known in the art of portable ruggedized equipment. Cap 14may also serve to reduce damage to dosimeter 10 from electrostaticdischarge (ESD), and may provide electromagnetic interference (EMI)shielding.

Housing 12 may include a loop 16 so that dosimeter 10 can easily beattached by way of a clip to a user's belt, for example. Housing 12 issized so as to be portable and conveniently carried by a user. Housing12 may have a size similar to a pager. For example, housing 12 may havea width of approximately 85 mm, a width of approximately 65 mm, and aheight of approximately 20 mm.

Cap 14 may be provided with indicator lights 18 that serve to notify theuser of the status of dosimeter 10. A green indicator light 18 can serveto indicate that dosimeter 10 is functioning properly, while a redindicator light 18 can serve to indicate that there is a malfunctionwith dosimeter 10. Cap 14 may also include a touch sensor 20 and anassociated cap printed circuit board (not shown) that provideselectronic components that provided support for indicator lights 18 andtouch sensor 20. Touch sensor 20 provides a way for the user to interactwith dosimeter 10 in order to check the status, activate firmwareupdates, and communicate with other devices, for example.

Cap 14 may also be provided with a charging port 21 that allows forrecharging of a battery 22 provided within housing 12. In certainembodiments, battery 22 is a single cell Lithium polymer (LiPo) batteryproviding approximately 500 mAh. Having a rechargeable battery providesportability and reliability for dosimeter 10.

A printed circuit board 24 is seated in housing 12. A photomultiplier 26is operably connected to printed circuit board 24 in known fashion. Incertain embodiments, photomultiplier 26 may be a Silicon (Si)photomultiplier. Printed circuit board 24 may house various electroniccomponents including, for example, a temperature sensor, amicrocontroller, an amplifier, a bias generator, and comparators, eachof which works to process light signals transmitted by photomultiplierto provide a measurement of gamma ray and neutron radiation. Printedcircuit board 24 includes communication capabilities that allowdosimeter 10 to communicate within a cloud computing network or othersuitable networks as described in greater detail below. Other suitablecomponents for printed circuit board 24 will become readily apparent tothose of skill in the art, given the benefit of this disclosure.

A scintillator 28 is positioned adjacent photomultiplier 26.Scintillator 28 may be formed of Cerium (Ce)-activated lithiumaluminosilicate glass. An exemplary scintillator is the 6-lithiumenriched GS20® glass scintillator provided by Scintacor of Cambridge,United Kingdom. In the illustrated embodiment, scintillator 28 takes theform of a block of (Ce)-activated lithium aluminosilicate glass. Asdescribed in greater detail below, the scintillator may take otherforms.

The term “adjacent” as used herein is meant to mean that two elementsare next to, or nearby one another. In some embodiments two adjacentelements may be in contact with one another or spaced slightly apartfrom one another.

In certain embodiments, scintillator 26 is a cube having a width ofapproximately 3.7 mm, a length of approximately 3.7 mm, and a height ofapproximately 3.7 mm.

An optical coupling 30 may be positioned between scintillator 28 andphotomultiplier 26. Optical coupling 30 serves to secure scintillator 28and photomultiplier 26 to one another while allowing light fromscintillator 28 to be transmitted to photomultiplier 26. In certainembodiments, optical coupling 30 may be achieved using a refractiveindex matching glue, such as those from Norland Products, Inc., or NTTAdvanced Technology Corporation. In certain embodiments, opticalcoupling 30 has a refractive index that is approximately equal to arefractive index of scintillator 28.

In certain embodiments, a surface of scintillator 28 facingphotomultiplier 26 (not visible here) may be polished in order toimprove the optical contact between scintillator 28 and photomultiplier26 and to avoid reflection of light that should be transmitted tophotomultiplier 26. In certain embodiments, the remaining surfaces ofscintillator 28 may be painted white in order to reflect light.

In the same or other embodiments, an optical reflector 34 may bepositioned about and substantially surround the surfaces of scintillator28, except for the surface of scintillator 28 facing photomultiplier 26.Optical reflector 34 serves to prevent light from being transmittedanywhere other than toward photomultiplier 26. Optical reflector 34 maybe formed of polytetrafluoroethylene, for example. In certainembodiments, optical reflector 34 may be a tape wrapped in layers aboutscintillator 28. Optical reflector 34 may be 80 μm thick in certainembodiments. It is to be appreciated that optical reflector 34 may takeon shapes other than a tape, such as a pre-formed can, dome, orconformal shape to scintillator 28, for example. Other suitable formsfor optical reflector 34 will become readily apparent to those skilledin the art, given the benefit of this disclosure.

Printed circuit board 24 may include a cable 40, such as a flat cable,for example, that serves to provide power and data transmission to andfrom printed circuit board 24. In some embodiments, cable 40 operativelycouples to printed circuit board 24 via a port opening in housing 12(not shown), where cable 40 is detachable from printed circuit board 24.In some embodiments, cable 40 can be used during the manufacture, test,or upgrade process for dosimeter 10. Alternately, cable 40 can be usedfor direct transfer of data from dosimeter 10 to network 66.

In certain embodiments, as shown in FIG. 2, an energy filter 42 may beprovided in dosimeter 10, which serves to help distinguish between theenergy sources being detected, i.e., distinguishing between gamma raysand neutrons. Embodiments of energy filter 42 may be configured as acube substantially surrounding scintillator 28, may be operativelycoupled to circuit board 24, and may be formed of gadolinium. Forexample, energy filter 42 may substantially surround scintillator 28 andphotomultiplier 26 (e.g. except for the surface of photomultiplier 26coupled to circuit board 24). It will, however, be appreciated thatfilter 42 can be configured in a variety of possible shapes, such as ashape that may conform to the shape of scintillator 28 and/or opticalreflector 34.

In embodiments that include energy filter 42, dosimeter 10 is effectivein detecting both gamma rays and neutrons. The light pulses created byscintillator 28 are converted into electrical signals by photomultiplier26 and then compared to reference signals in known fashion to provideaccurate levels of the radiation detected.

In certain embodiments dosimeter 10 does not include energy filter 42.In such embodiments dosimeter 10 provides accurate levels of the gammaray radiation, however, dosimeter 10 does not provide accurate levels ofneutron radiation without energy filter 42. Neutrons tend to create astrong over-response, which provides an indication of the presence ofneutrons, but not an accurate level of their presence. Thus, in such anembodiment, dosimeter 10 acts as an alarm for neutron radiationexposure, indicating to the user, and others, high levels of neutronexposure without specifying a numeric value for the neutron radiationlevel present. In such an embodiment, dosimeter 10 can produce anaudible signal and/or vibration signal to indicate to the user a highlevel of neutron radiation, thereby providing a level of safety andsecurity for the user.

In certain embodiments, as shown in FIG. 3, energy filter 42 may includea plurality of apertures 43 that extend through energy filter 42.Apertures 43 may allow some low energy gamma ray radiation in toscintillator 28. Apertures 43 may be drilled through one or more of thesurfaces of energy filter 42. In certain embodiments, apertures 43 arearranged in a matrix of rows and columns of apertures 43.

In certain other embodiments, scintillator 28 is not a pre-formed blockof material, and may be formed in place directly on top ofphotomultiplier 26, as shown in FIG. 4. In certain embodiments,scintillator 28 is formed of a powder. In this embodiment, a container44 with an open bottom and top is seated on photomultiplier 26. A powder45 of Cerium (Ce)-activated lithium aluminosilicate glass that formsscintillator 28 is deposited within container 44 directly on top ofphotomultiplier 26. After powder 45 is deposited in container 44, anoptical glue (not shown here) is deposited in container 44 and serves tofill the gaps between the particles of powder 45, secure the particlestogether, and secure the particles to photomultiplier 26. After powder45 and the optical glue have set, container 44 can be removed andoptical reflector 34 can be positioned on scintillator 28 as discussedabove.

In other embodiments, as shown in FIG. 5, container 44 is not removed,and a cover 46 is secured to the open top of container 44. In such anembodiment, container 44 and cover 46 are formed of a reflectivematerial, such as aluminum, DF2000MA (available from 3M), or SteinerfilmK (available from Steiner GmbH & Co KG), for example. In the presentlydescribed example, embodiments of container 44 and cover 46 formed of areflective material act as an optical reflector in the same way asdescribed above with respect to optical reflector 34.

It is to be appreciated that the small size of dosimeter 10 reduces thetravel time for the photons within dosimeter 10, and reduces lightlosses. The smaller size provides for reduced reflections on the wallsof scintillator 28. Additionally, the use of Ce-activated lithiumaluminosilicate glass reduces the chances of afterglow after excitationwith high gamma doses.

A Ce-activated lithium aluminosilicate glass scintillator provides thesame pulse shape when excited by electrons or charged particles and,therefore, the distinction or discrimination between gammas and neutronsis done on the basis of pulse height rather than pulse shape.

The processing of the signal from dosimeter 10 is performed by way ofsemi-spectroscopic counter hardware or by a multi-channel analyzer (MCA)using a single signal path that uses pulse height analysis.

It is to be appreciated that in certain embodiments, a plurality ofdosimeters 10 will be provided. For example, in a facility with a largenumber of workers and a potential for exposure to gamma ray or neutronradiation, each individual may be outfitted with their own dosimeter 10when they are in environments with potential exposure to radiation. Thesmall size and portability of dosimeter 10 makes such an implementationpossible.

Additionally, in such a facility, a plurality of repeaters may beinstalled in particular locations. The repeaters can collect data fromany nearby dosimeters 10 and forward that data to network 66 to helpensure that the data regarding radiation levels from dosimeters 10 getstransferred to the proper location. The repeaters and dosimeters 10 maybe connected through network 66 so that real-time data regarding doselevels for all individuals can be provided and reviewed at multiplelocations.

As shown schematically in FIG. 6, a plurality of dosimeters 10 (carriedby user's) are shown positioned throughout a facility 60. Facility 60may be an individual building with rooms therein, as illustrated in FIG.6. In other embodiments, facility 60 could include a plurality ofbuildings, and each of those buildings could have one or more roomstherein. In still other embodiments, facility 60 could be onboard a shipor other vessel where there is a need to monitor radiation dose levels.

In addition to dosimeters 10, a plurality of repeaters 62 may be locatedwithin facility 60 as well. As noted above, repeaters serve to collectradiation data transmitted by dosimeters 10 and forward this data. Forexample, repeaters 62 may be located at each entrance and exit 64 infacility 60 to ensure that readings of dose levels of individuals asthey enter and exit facility 60 are transmitted to a computer network,as described below. Additionally, repeaters 62 may be located in highradiation areas where the risk of exposure is greater than in otherareas of facility 60. These repeaters 62 provide an enhanced level ofsecurity and safety for the individuals within facility 60.

As the user moves throughout facility 60, the individual dosimeter 10carried by the user can be used to track radiation levels for that user,which data can be used in a real-time basis to provide a warning to theuser when a particular radiation level has been exceeded. The term“real-time” as used herein typically refers to reporting, depicting, orreacting to events at the same rate and sometimes at the same time asthey unfold (e.g. within a few seconds or fractions of a second), ratherthan delaying a report or action. This data can also be viewed by othersin remote locations through a computer network, described in greaterdetail below.

Dosimeters 10 and repeaters 62 may be connected to a computer network 66in a cloud computing environment 68 as illustrated in FIG. 7. Cloudcomputing environment 68 may include one or more computing devices 70,each of which may include computing resources. In some embodiments,computing resources may include any hardware and/or software used toprocess data. For example, computing resources may include hardwareand/or software capable of executing algorithms, computer programs,and/or computer applications. In some implementations, exemplarycomputing resources may include application servers and/or databaseswith storage and retrieval capabilities. Each computing device 70 may beconnected to any other computing device, any repeaters 62, and anydosimeter 10 in cloud computing environment 68 by way of computernetwork 66.

Cloud computing environment 68 may include a resource manager 72, whichmay be connected to computing devices 70 over computer network 66. Insome implementations, resource manager 72 may facilitate the provisionof computing resources by one or more computing devices 70 to one ormore dosimeters 10 or repeaters 62. Resource manager 72 may receive arequest for a computing resource from a particular dosimeter 10 orrepeater 62. Resource manager 72 may identify one or more computingdevices 70 capable of providing the computing resource requested by thedosimeter 10 or repeater 62. Resource manager 72 may facilitate aconnection between a computing device 70 and a particular dosimeter 10or repeater 62.

Computing devices 70 may any of various forms of digital computers, suchas laptops, desktops, workstations, personal digital assistants,servers, blade servers, mainframes, and other appropriate computers.Computing devices 70 may also be any kind of mobile computing devicesuch as personal digital assistants, cellular telephones, smart-phones,and other similar computing devices. The components shown here, theirconnections and relationships, and their functions, are meant to beexamples only, and are not meant to be limiting.

Computing devices 70 in known fashion may include a processor, a memory,a storage device, interfaces connecting to the memory and the storagedevice, and a display so that data regarding radiation exposure levelsof the various users is visible to others. The processor can processinstructions for execution within computing device 70, includinginstructions stored in the memory or on the storage device to displaygraphical information for a GUI on an external input/output device, suchas a display. In other embodiments, multiple processors may be used, asappropriate, along with multiple memories and types of memory. Also,multiple computing devices may be connected, with each device providingportions of the necessary operations (e.g., as a server bank, a group ofblade servers, or a multi-processor system).

[1] Computing devices 70, resource manager 72, dosimeters 10, andrepeaters 62 may communicate wirelessly where necessary using variousmodes or protocols such as GSM voice calls (Global System for Mobilecommunications), SMS (Short Message Service), EMS (Enhanced MessagingService), or MMS messaging (Multimedia Messaging Service), CDMA (codedivision multiple access), TDMA (time division multiple access), PDC(Personal Digital Cellular), WCDMA (Wideband Code Division MultipleAccess), CDMA2000, or GPRS (General Packet Radio Service), among others.In addition, short-range communication may occur, such as using aBluetooth®, Wi-Fi™, or other such transceiver (not shown).

Those having skill in the art, with the knowledge gained from thepresent disclosure, will recognize that various changes can be made tothe disclosed apparatuses and methods in attaining these and otheradvantages, without departing from the scope of the present disclosure.As such, it should be understood that the features described herein aresusceptible to modification, alteration, changes, or substitution. Forexample, it is expressly intended that all combinations of thoseelements and/or steps which perform substantially the same function, insubstantially the same way, to achieve the same results are within thescope of the embodiments described herein. Substitutions of elementsfrom one described embodiment to another are also fully intended andcontemplated. The specific embodiments illustrated and described hereinare for illustrative purposes only, and not limiting of that which isset forth in the appended claims. Other embodiments will be evident tothose of skill in the art. It should be understood that the foregoingdescription is provided for clarity only and is merely exemplary. Thespirit and scope of the present disclosure is not limited to the aboveexamples, but is encompassed by the following claims. All publicationsand patent applications cited above are incorporated by reference intheir entirety for all purposes to the same extent as if each individualpublication or patent application were specifically and individuallyindicated to be so incorporated by reference.

1.-22. (canceled)
 23. A dosimeter comprising: a housing; a printedcircuit board positioned within the housing; a silicon photomultiplieroperably connected to the printed circuit board; a scintillator formedof a glass powder and positioned on the silicon photomultiplier, whereinthe scintillator comprises a glue distributed throughout the glasspowder to secure particles together and to the silicon photomultiplier,and further wherein the distribution of the glue comprises an opticalcoupling between the scintillator and the silicon photomultiplier; and;an optical reflector surrounding the scintillator.
 24. The dosimeter ofclaim 23, wherein the scintillator comprises a block form.
 25. Thedosimeter of claim 24, wherein a surface of the block form facing thesilicon photomultiplier is polished.
 26. The dosimeter of claim 24,wherein a plurality of surfaces of the block form are painted white. 27.The dosimeter of claim 23, wherein the optical reflector comprises areflective container substantially surrounding the glass powder.
 28. Thedosimeter of claim 27, wherein the optical reflector comprises areflective cap secured about an opening of the container.
 29. Thedosimeter of claim 23, wherein a refractive index of the glue isapproximately equal to a refractive index of the scintillator.
 30. Thedosimeter of claim 23, wherein the optical reflector is formed ofpolytetrafluoroethylene.
 31. The dosimeter of claim 23, wherein theoptical reflector comprises a tape form.
 32. The dosimeter of claim 23,wherein the housing is formed of aluminum.
 33. The dosimeter of claim23, further comprising a filter surrounding the scintillator and thesilicon photomultiplier.
 34. The dosimeter of claim 33, wherein thefilter is formed of gadolinium.
 35. The dosimeter of claim 33, whereinthe filter includes a plurality of apertures extending therethrough. 36.The dosimeter of claim 23, wherein the housing is sealed with an epoxysealant.
 37. The dosimeter of claim 36, wherein the epoxy sealant isblack.
 38. The dosimeter of claim 23, further comprising a cableoperably connected to the printed circuit board and configured to supplypower to the printed circuit board and provide digital datacommunication with the printed circuit board.
 39. A dosimeter systemcomprising: a computer network including a plurality of computingdevices; a plurality of dosimeters, each dosimeter comprising: ahousing; a printed circuit board positioned within the housing andconfigured to communicate with the computer network; a siliconphotomultiplier operably connected to the printed circuit board; ascintillator formed of a glass powder and positioned on the siliconphotomultiplier, wherein the scintillator comprises a glue distributedthroughout the glass powder to secure particles together and to thesilicon photomultiplier, and further wherein the distribution of theglue comprises an optical coupling between the scintillator and thesilicon photomultiplier; and; an optical reflector surrounding thescintillator; and a plurality of repeaters configured to receive datafrom the dosimeters and transmit that data to the computer network. 40.A method of forming a scintillator comprising: seating a container withan open bottom on a photomultiplier; depositing a glass powder withinthe container on top of the photomultiplier; and depositing a glue inthe container.
 41. The method of claim 40, wherein: the glue fills gapsbetween particles of the powder.
 42. The method of claim 41, wherein:the glue secures the particles together.
 43. The method of claim 41,wherein: the glue secures the particles to the photomultiplier.
 44. Themethod of claim 41, further comprising: removing the container; andpositioning an optical reflector on the scintillator.
 45. The method ofclaim 40, further comprising: securing a cover on top of the container.46. The method of claim 45, wherein: the cover comprises a reflectivematerial.
 47. The method of claim 46, wherein: The reflective materialcomprises aluminum or Steinerfilm K.
 48. The method of claim 40,wherein: the container comprises a reflective material.